As early as 1200's there was a serious attempt to regulate the purity of precious metals in England, and wasn't until the year 1300, in the reign of Edward I, that the first statute was passed. Part of it stated:
"It is ordained that no goldsmith of England or elsewhere in the lordship of the king...and that no kind of plate of silver leave the hands of the workmen until it is assayed by the wardens of the craft [The Goldsmiths Company] and that it be signed with a leopard’s head; that no one work worse gold than the assay of Paris,[a gold standard of that time of 19.2 carat] and that the wardens of the craft go from shop to shop among the workmen, testing that the gold is the same as the aforesaid assay, and if they find any worse than the assay, that the work be forfeit to the king."
'Leopards Head'... or Kings Mark, was the emblem struck by the wardens [later, The Goldsmiths Company] to signify the article reached the required purity. On receiving its royal charter in 1327 The Goldsmiths Company, a London Livery, set up in permanent premises at Foster Lane, City of London, becoming the first English Assay Office. GOLDSMITHS HALL in Foster Lane, London, is still the home of the London Assay Office today and they still use the leopards head as their Assay Office mark over 700 years later. It is part of The British Hallmarking Council, an executive non-departmental public body.
The Crown Mark is applied to any item that is made from a solid gold alloy, not gold plated...gold plating, rolled gold, gold filled etc. means nothing in precious metal terms and virtually is worthless. In the UK there are five qualities of gold able to be hallmarked, 24 carat (999 parts gold) 22 carat (916 parts gold), 18 carat (750 parts gold), 14 carat (585 parts gold) and 9 carat (375 parts gold). But what does carat mean? Pure gold (or silver) has no impurities and is classified as having 999 parts pure gold. In contrast 18 carat has 750 parts pure gold with 250 parts alloy. It is marked 
in the hallmark. When assayed, if the assay comes back as, say, 749 rather than 750, the assay fails and the article will not be able to be marked as 18ct...In such cases the next lower carat is marked. ie 14 carat. If 9 carat fails the assay it is destroyed.
Alloys are added to precious metals to provide better wearing characteristics.
Gold being melted and alloyed in our studio to make 18ct yellow gold used to make the leaves and wire in one of the tiaras. When we melt and alloy any metal we always add a little extra 24 carat fine gold to the mix to give a high assay of 755 or more so we can be assured of it's purity count when being hallmarked.
The Sterling Silver Lion. As with the gold standard, pure silver is classed as containing 1000 parts of pure metal, in this case of course silver. Sterling silver, has a minimum of 925 pure silver and 75 parts alloy, usually copper. It is marked 925 in a shield like so...
The final mark is the Date Mark. Formed of a single letter in a shield. The shield, along with the letter, is changed every year. This can, as does, make analysing hallmarks difficult as they are monstly small, look very similar under magnification in sheild-shape and font style. A slight error in analysing them and you could be many years out.
We are proud to say that we've had all our pieces assayed and marked, by hand, at this prestigious and historic establishment, The London Assay Office.
Our finished hallmark on one of the tiaras. Hand struck at the London Assay Office. Being hand struck means slight discrepancies in the alignment of the marks showing that humans aren't as perfect as machines, a good thing when it comes to art.
As with the mis-aligned marks when hallmarking, the pressure caused when striking the metal punches causes planishing marks on the rear side. Rather than re-work the metal we left them visible as another sign of our tiaras being handmade..
The above is just a snippet of hallmarking and its many facets. More information can be seen here on The Goldsmiths Company website. The Goldsmiths Company.
